Electrochemical Trifluoromethylation of Glycals

Abstract

Carbohydrates play essential roles in various physiological and pathological processes. Trifluoromethylated compounds have wide applications in the field of medicinal chemistry. Herein, we report a practical and efficient trifluoromethylation of glycals by an electrochemical approach using CF3SO2Na as the trifluoromethyl source and MnBr2 as the redox mediator. A variety of trifluoromethylated glycals bearing different protective groups are obtained in 60–90% yields with high regioselectivity. The successful capture of a CF3 radical indicates that a radical mechanism is involved in this reaction.

Recent advances in transition metal-mediated trifluoromethylation reactions

“…In their work, they employed CF 3 SO 2 Na as a radical trifluoromethylating source and MnBr 2 as a redox mediator to achieve a variety of trifluoromethylated glycals bearing different protectives in 60-90% yields with high regioselectivity (Scheme 85). 157…”

The Synthesis and Glycoside Formation of Polyfluorinated Carbohydrates

“…158 Many syntheses of lactal are available, for example via peracetylation of lactose, anomeric bromination and elimination with Zn. 159 Compared to reaction with peracetylated glucal, reaction of 13 with CF3OF was reported to require a higher temperature, and proceeded with a different facial selectivity. The syn-addition products arising from the b-face approach, the 2-epilactosyl products 14 and 16, are now the major isolated isomers, which was explained by the steric influence of the second monosaccharide ring.…”

Catalytic Radical Reactions of Unsaturated Sugars

“…[56] Then fragmentation with loss of dibenzothiophene To provide a more applicable and sustainable route for the trifluoromethylation of glycals, the same research group have recently developed an electrocatalytic protocol using CF 3 SO 2 Na as an inexpensive, readily available, and benchstable trifluoromethyl source (Scheme 7). [57] The reaction was performed in an undivided cell with two Pt electrodes as the anode and the cathode, using catalytic MnBr 2 as redox mediator. The reaction efficiently enabled the trifluoromethylation of d-galactals, d-glucals, l-arabinals, l-rhamnals and d-xylals bearing benzyl, p-methoxybenzyl or tertbutyldimethyl silyl protecting groups (64-85 % yield), while the more electron poor peracetylated d-galactal revealed to be a challenging substrate (30 % yield).…”